Image adjusting device for offset printing machine

Abstract

An image adjusting device for an offset printing machine includes a drive source, an adjustment gear mounted on a rotary shaft and always engaged with a gear mounted on a blanket cylinder for adjusting a position of an image to be printed, a clutch mechanism for selectively transmitting a rotation of the drive source to the adjustment gear, and an encoder for controlling a rotational amount of the adjustment gear, the encoder being mounted on the rotary shaft. Further the image adjusting device has first and second detectors for detecting the rotational positions of the blanket cylinder and a cylinder gear, respectively, a microcomputer provided with calculating means for calculating standard and present phase differences between the blanket cylinder and the cylinder gear, and an input means for inputting an amount of adjustment on the basis of the present phase difference therebetween. Thus, it is possible to more correctly effect the image adjustment in the offset printing press.

What is claimed is: 
     
       1. An image adjusting device for an offset printing machine, comprising: a drive source for driving a gear transmission mechanism by which a phase difference between a cylinder and a cylinder gear for rotating the cylinder is changed;   an adjustment gear always engaged with the cylinder gear which is mounted on said cylinder for adjusting a position of an image to be printed;   a rotational clutch mechanism for selectively transmitting a rotation of the drive source to said adjustment gear for adjusting the phase difference between the cylinder and the cylinder gear; and   a rotational amount control means for controlling a rotational amount of said adjustment gear, said rotational amount control means being mounted at a first end of a rotary shaft on which said adjustment gear is mounted at a second end.   
     
     
       2. An image adjusting device according to claim 1, wherein said clutch mechanism includes a pair of first and second spur gears which are arranged coaxially with each other adjacent to each other and a third spur gear which is always engaged with said first spur gear, said third spur gear being movable in an axial direction of said pair of spur gears for transmitting a rotation of said first spur gear to said second spur gear. 
     
     
       3. An image adjusting device according to claim 2, further comprising an axially moving means for drivingly moving said third gear in its axial direction, said axially moving means including a solenoid for selectively moving said third spur gear in a first direction, a spring biasing means for moving said third spur gear in a second direction, and a link mechanism interposed between said solenoid and said spring biasing means. 
     
     
       4. An image adjusting device according to claim 1, wherein said rotational amount control means includes a rotary encoder for detecting an exact rotational amount of said adjustment gear. 
     
     
       5. An image adjusting device according to claim 4, wherein said rotary encoder starts to detect said exact rotational amount after said third spur gear is engaged with said second spur gear. 
     
     
       6. The image adjusting device according to claim 5, wherein said drive source comprises a motor. 
     
     
       7. An image adjusting device for an offset printing machine, comprising: a drive source for driving a gear transmission mechanism by which a phase difference between a cylinder and a cylinder gear for rotating the cylinder is changed;   a first detecting means for detecting a rotational position of the cylinder;   a second detecting means for detecting a rotational position of the cylinder gear;   a calculating means for calculating a standard phase difference between the cylinder and the cylinder gear when the cylinder and the cylinder gear are located at their respective standard positions and a present phase difference therebetween;   a memory means for memorizing the standard and present phase differences therebetween;   an input means for inputting an amount of adjustment on the basis of the present phase difference therebetween; and   a rotational control means for controlling the gear transmission mechanism to change the present phase difference therebetween in response to the amount of adjustment inputted through the input means.   
     
     
       8. An image adjusting device according to claim 7, further comprising a display for displaying the present phase difference on the basis of the standard phase difference. 
     
     
       9. An image adjusting device according to claim 7, wherein said calculating means includes a standard point memorizing button and said calculating means starts to calculate the standard phase difference after said standard point memorizing button is pushed. 
     
     
       10. An image adjusting device according to claim 7, wherein said first detecting means comprises a proximity switch provided on a frame and a rotary detection bar fixed to an axis of the cylinder, and said second detecting means comprises a proximity switch provided on the frame and a rotary detection bar fixed to an axis of another cylinder rotated in synchronism with the cylinder, the rotational position of said rotary detection bar of said second detecting means being representative of the rotational position of the cylinder gear. 
     
     
       11. An image adjusting device according to claim 7, wherein said input means includes ten keys. 
     
     
       12. An image adjusting device according to claim 7, wherein said calculating means for calculating the standard and present phase differences counts number of pulses generated by an encoder which is provided in the gear transmission mechanism from when the first detecting means is turned on to when the second detecting means is turned on. 
     
     
       13. An image adjusting device according to claim 7, wherein said gear transmission mechanism includes an adjustment gear always engaged with the cylinder gear which is mounted on the cylinder for adjusting a position of an image to be printed, a rotational clutch mechanism for selectively transmitting a rotation of the drive source to said adjustment gear for adjusting the phase difference between the cylinder and the cylinder gear and a rotational amount control means for controlling a rotational amount of said adjustment gear, said rotational amount control means being mounted at a first end of a rotary shaft on which said adjustment gear is mounted at a second end. 
     
     
       14. An image adjusting device according to claim 13, wherein said clutch mechanism includes a pair of first and second spur gears which are arranged coaxially with each other adjacent to each other and a third spur gear which is always engaged with said first spur gear, said third spur gear being movable in an axial direction of said pair of spur gears for transmitting a rotation of said first spur gear to said second spur gear.